Edward davis



(No Model.)

DAVIS. TBLEP-HQNE.

Patented l2, 1890.

No. 435x981.`

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UNITED STATES- PATENT" OEEIcE.

EDWARD DAVIS, or CAMBRIDGE, MASSACHUSETTS, ASsIeNoR oF ONEIIALF To E. R. WELCH, or SAME PLACE. i

TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 433,981, dated August 12, 1890. Application filed November 19, 1885. Renewed February 14, 1887. Serial No. 227,604. (No model.)

To all whom it may concern:

Be it known that I, EDWARD DAVIS, of Cambridge, in the county of Middlesex and State of MaSsachusetts,have invented certain new and useful Improvements in Telephones, of

which the following isa specification.

This invention has for its object, first, to reenforce the receiving instrument or telephone of a telephone-circuit, and thus increase the.

ro eect of its sound vibrations, and also provide a telephonie instrument capable of being used either in a circuit to re-enforce a receiving-telephone, and thusincrease the sound sent over the line from a transmitting-instrument or a transmitting or receiving telephone, its principal use, however, being to reenforce a receiving-telephone,

To these ends my invention consists, first, in the combination, with the main line of a 2o telephone-circuit, an induction-coil, the secondary of which is included therein, of a reenforcing apparatus consisting of a polarized electro-magnet included in the main line, two diaphragms separated by a space contain- 2 5 ing powdered carbon or other variable resistance, one of said diaphragms being in close proximity to the electro-magnet, and a primary circuit comprising a battery, the primary of the induction-coil, and the two diaphragms, the arrangement being such that said re-enforcing apparatus intensities or strengthens the sound transmitted over the line at the receiving-telephone, said apparatus being also capable of being used as an 3 5 electric telephone for transmitting or receiving articulate sounds, all of which I will now proceed to describe and claim.

In the accompanying' drawings, forming 'a part of this specification, Figure 1 represents 4ov an elevation of the case or holder supporting the polarized electro-magnet, the diaphragms, and carbon filling. Fig. 2 represents a Section on line Y Z, Fig. 1. Fig. 3 represents an elevation of the opposite side of the casing from that shown in Fig. 1. Figs. 4, 5, and 6 are detached views of the diaphragms. Fig. 7 is a diagram of my improved circuit.

The same letters and figures of reference indicate the same parts in all the views. 5o In the drawings, 1 represents the line-wire `of a telephone-circuit having a transmitter (not shown) and a receiving or hand telephone T.

L represents a polarized electro-magnet, and. S an induction-coil located between the trans- 5 5 mitting and receiving instruments, the line passing through said electro-magnet ,'and through the secondary of the induction-coil.

G and F represent the two diaphragms supported by a case or holder, as hereinafter de- `6o scribed, and separated by a space containing a filling II of powdered carbon or other variable resistance. Said diaphraglns areincluded in a primary circuit composed of said diaphragms, the carbon iilling IjI, a battery V, the primary of the induction-coil, and Wires 2, 2', and 2", respectively, connecting the diaphragm G with one pole of the battery, the other pole of the battery with the primary of j the induction-coil, and the diaphragm F with 7o the primary of the induction-coil, said dia -phragms being the electrodes or terminals of the primary circuit.

The sound-waves, passing through the line and through the electro-magnet and the secondary of the induction-coil, act on the dia' phragm G and the primary circuit, of which Said diaphragms form a part, to cause variations of the strength of the battery in said circuit, which act inductively to cause an un- 8o dulating current in the secondary of the induction coil. This undulating current is added to that sent forth by the induction-coil, and therefore Ire-enforces the receiving-telephone and greatly increases the effect of the sound-Waves, making the speech much louder and clearer than that transmitted by any other apparatus of which I am aware, heretofore or now in use. y

Referring to Figs. l, 2, 3,4, 5, and 6, A rep- 9o res'ents a ring of non-conducting material having an internal shoulder A', which Serves to support and keep apart the diaphragms F G,

Ethe space between Said plates containing the powdered carbon II. A circular plate of metal 9 5 B, with a central perforation, as shown,is secured to one face of ring Aby means of screws B', and between said plate andthe diaphragm F is inserted a ring E, so that, onscrewing. down Screws B', plate B and ring E will press Ioo diaphragm F against shoulder A', and thereby secure said diaphragm firmly in place, while,

by the insertion of ring E, a shallow chamber is formed between the plate B and diaphragm F, as is usual in magnetic telephones or receivers. The diaphragm G is held in place against shoulder A by means of screws I', and a ring I, pressed by said screws firmly against said plate, as shown in Fig. 2. The diaphragms F G are preferably'provided on theirinner sides with points or projections F' G', preferably of platinum or otherrefractory conductor, the preferred arrangement of these points being shown in detail in Figs. 4, 5, and 6. As shown, in this case plateF is provided with one row of points F', while plate G has two rows G', so that when said plates are in position in the telephone, as shown in Fig. 6, there will be `three concentric rows of point-s, one row attached to plate F and two to plate G. The practical effect of this arrangement is to increase the area of contact of the plates with the carbon placed between; also, to prevent the packing of the carbon. It is not necessary to adhere to precisely the described form or arrangement of the points on said plates. The number and form of said points or projections maybe greatly varied without departing from the principle involved. If desired, the points may be placed on but one of the diaphragms as when one diaphragm is made of a very thin piece of platinum or other conducting metal.

The permanent magnet L, preferably of the curved form shown in Fig. 3, is secured to frame A, and has attached to one of its poles the electro-magnet K, which is in close proximity to the diaphragm G, the magnet L, electro-magnet K, and diaphragm G being relatively arranged,- as in a magnetic telephone.

Four binding-posts D D D D', secured to frame A, are connected one to each of dia- 'phragms F G, and the other twoto the terminals of electro-magnet K.

My invention is not limited to the described details of construction, as the polarized magnet, the diaphragms, and the carbon filling may be supported by any other suitable means.

The instrument shown in Figs. 2 and 3 may be used as a telephonie transmitter, and when so used is preferably provided with a trumpetshaped mouth-piece C to concentrate the sounds of the speakers voice and conduct them against the diaphragm F. WVhen the instrument is thus used, the variations of pressure on the'ycarbon H, caused by the soundwaves impinging on the diaphragm F, cause Variations of resistance, and therefore ofcurrent in the primary of the induction-coil S, which variations act inductively to cause an undulating current in the secondary of said coil, and therefore in line 1, as with all carbon telephones or transmitters. At the same time the electro-magnetic effects produced by the vibrations of diaphragms F G in close proximity to the pole of magnets L and K also produces an undulatory current, which is added to that sent forth by the inductioncoil S, as before described. It is also probable that as diaphragms F G and tlie'contained carbon II form a movable conductor carryinga current and moved into and out of a magnetic field by the.action of the soundwaves that this may also add to the effect, according toy well-known law. This would add to the variation of the current in the primary of the induction-coil S, and therefore to the undulatory current in the line l. The practical effect of this arrangement is to produce a telephonie transmitter of great power, and transmitting speech much louder and clearer than the ordinary transmitter now in use. It is obvious that the direction of the current may be reversed and the diaphragms F G be used in a receiver instead of a transmitter without departing from the spirit of my invention. Y

The entire apparatus described may be duplicated or multiplied, as may be desired, to increase the effect of the sound-vibrations and adapt the apparatus to long-distance telephoning.

I am aware that powdered `carbon confined by a diaphragm has been before used in connection with a telephonie' transmitter. I am also aware that a diaphragm vibrating in proximity to the poles of au electro-magnet for the purpose of transmitting articulate speech is not new.

I am aware of the constructions disclosed by the United States Patent No. 272,329, granted February 13, 1883, to Rose and Cheever, of Patent No. 292,203, granted January 24, 1884, to Cheever, and of No. 231,239, granted August 17, 1880, to Rose; and I do not therefore claim, broadly, any feature disclosed in either of said patents.

I do not desire to claim herein the described method of increasing the current in the line to increase the amplitude of vibration in a telephone receiver, as the same forms the subject-matter of another application filed January 8, 1887, Serial No. 223,746.

1. In an electric telephone, the combination, with a resistance material, such as powdered carbon, a diaphragm in contact withV the same, an electro-magnet arranged in proximity to said diaphragm, so as to act upon it, an electric circuit containing a battery, the resistancevaryiug material, and theprimary of an induction-coil, of a main line, including the electro-magnet, the secondary of the induction-coil,.and ya telephone-receiver, said electro-magnet diaphragm and resistance material being so arranged relatively that a current in the main line will produce a current of opposite polarity in the primary circuit of the induction-coil, as set forth.

2. In an electric telephone with a mass of semi-conducting material, two conducting diaphragms confining said material, an electro-magnet arranged in proximity to one of the diaphragms, a circuit containing a bat- IOO IIO

tery, the semi-conducting material, and the In testimony whereof have signed my primary of an induction-coil, of a main line, name to this specification, in the presence of xo including the electro-magnet, thev secondary two subscribing Witnesses, this 16th day 0f of the induction-coil, and a telephonc-re- November, 1885.

5 cever, the diaphragm opposite the one acted l EDWARD DAVIS.

upon by the .electro-magnet being arranged Vitnesses: to receive and be acted upon by Vibrations C. F. BROWN,

of the air, substantially as described. H. BROWN. 

